Merge branch '2.3.x' into 2.4.x

Closes gh-24626

buildSrc/src/main/resources/NOTICE.txt

 Spring Boot ${version}
-Copyright (c) 2012-2020 Pivotal, Inc.
+Copyright (c) 2012-2021 Pivotal, Inc.
 
 This product is licensed to you under the Apache License, Version 2.0
 (the "License"). You may not use this product except in compliance with

eclipse/eclipse.properties

-copyright-year=2012-2020
+copyright-year=2012-2021

spring-boot-project/spring-boot-docs/src/docs/asciidoc/index-docinfo.xml

 <productname>Spring Boot</productname>
 <releaseinfo>{spring-boot-version}</releaseinfo>
 <copyright>
-	<year>2012-2020</year>
+	<year>2012-2021</year>
 </copyright>
 <legalnotice>
 	<para>

spring-boot-project/spring-boot-docs/src/docs/asciidoc/legal.adoc

@@ -3,7 +3,7 @@
 
 {spring-boot-version}
 
-Copyright © 2012-2020
+Copyright © 2012-2021
 
 Copies of this document may be made for your own use and for distribution to
 others, provided that you do not charge any fee for such copies and further